Distributed control system including a compact easily-extensible and serviceable field controller

ABSTRACT

A field controller for use in a distributed control system including an area controller and at least one field controller. The field controller manages at least one controlled device in an industrial process operation. The field controller comprises a processor module segment through which it can control a selected number of devices, and it may also include one or more expansion module segments to enable it to control a larger number of controlled devices. The processor module segment includes a processor module and at least one local interface module for interfacing to a controlled device, and the expansion module segment includes interface modules for interfacing to other controlled devices. In the processor module segment, the processor module and said local interface module are interconnected by a bus segment, which is also connected to an upstream off-module connector. Each expansion module segment includes at least one interface module, and also includes a downstream off-module connector and an upstream off-module connector, which are interconnected by a bus segment. The downstream off-module connector of each expansion module segment is adapted to mate with the upstream off-module connector of the processor module segment and of other expansion module segment, so as to facilitate the interconnection of the processor module segment and a sequence of expansion module segments by establishing a unitary multi-drop bus comprising the processor module&#39;s bus segment and the bus segments of expansion module in the sequence. The precessor module controls each controlled device through the respective local interface module or expansion interface module connected thereto. The processor module segment and each expansion module segment are each mounted in a housing segment which is configured to form a unitary housing when they are interconnected.

This application is a continuation of U.S. Ser. No. 08/560,167, filedNov. 20, 1995, entitled “DISTRIBUTED CONTROL SYSTEM INCLUDING A COMPACTEASILY-EXTENSIBLE AND SERVICEABLE FIELD CONTROLLER,” which claims thebenefit of priority of U.S. Serial No. 60/005,279, filed Oct. 10, 1995,entitled “DISTRIBUTED CONTROL SYSTEM INCLUDING A COMPACTEASILY-EXTENSIBLE AND SERVICEABLE FIELD CONTROLLER, the teachings of allof which are incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates generally to the field of digital data processingsystems, and more specifically to distributed monitoring and controlsystems which may be used in, for example, process control arrangementsfor controlling large industrial operations such as manufacturing plantsor chemical processing plants, environmental monitoring controlarrangements for controlling heating, air conditioning, ventilation,illumination, and other controllable environmental factors inindustrial, commercial and home environments. The invention particularlyprovides a controller (called herein a “field controller”) whichprovides a compact, computationally-powerful package which is convenientto install and service in a wide variety of environments.

BACKGROUND OF THE INVENTION

Distributed control systems are often used in a number of commercial,industrial and home applications, in particular to monitor and controloperations at manufacturing, chemical processing and similar industrialoperations, to monitor and control environmental and other factors andso forth. In a manufacturing operation, a distributed control systemwill typically control machines which facilitate the manufacture andassembly of the products being manufactured. In addition, in a chemicalprocessing operation, a distributed control system may control valves tocontrol rates of flow of chemicals into and out of reaction chambers,reaction temperatures and pressures and the like which are required tocarry out the chemical process. In addition, to controlling themanufacturing or chemical process, distributed control systems mayperform bookkeeping operations to keep track of the inventory of inputsrequired for the manufacturing or chemical process, as well as theinventory of outputs produced by the operation.

Typical distributed control systems essentially comprise large,centrally-located and expensive computer systems. A number of problemsarise out of use of such computer systems, including the facts that theyare expensive to maintain and typically have limited expansioncapabilities.

SUMMARY OF THE INVENTION

The invention provides a relatively compact, computationally powerful,easily-extendable and easily-serviceable field controller for use in avariety of industrial, commercial and home applications.

In brief summary, the invention provides a new field controller for usein a distributed control system including an area controller and atleast one field controller. The field controller manages at least onecontrolled device in an industrial process operation. The fieldcontroller comprises a processor module segment through which it cancontrol a selected number of devices, and it may also include one ormore expansion module segments to enable it to control a larger numberof controlled devices. The processor module segment includes a processormodule and at least one local interface module for interfacing to acontrolled device, and the expansion module segment includes interfacemodules for interfacing to other controlled devices. In the processormodule segment, the processor module and said local interface module areinterconnected by a bus segment, which is also connected to an upstreamoff-module connector. Each expansion module segment includes at leastone interface module, and also includes a downstream off-moduleconnector and an upstream off-module connector, which are interconnectedby a bus segment. The downstream off-module connector of each expansionmodule segment is adapted to mate with the upstream off-module connectorof the processor module segment and of other expansion module segment,so as to facilitate the interconnection of the processor module segmentand a sequence of expansion module segments by establishing a unitarymulti-drop bus comprising the processor module's bus segment and the bussegments of expansion module in the sequence. The processor modulecontrols each controlled device through the respective local interfacemodule or expansion interface module connected thereto. The processormodule segment and each expansion module segment are each mounted in ahousing segment which is configured to form a unitary housing when theyare interconnected.

A benefit of this arrangement is that the number of controlled deviceswhich can be controlled by the field controller be easily increased ordecreased by adding expansion module segments to, or removing them from,the field controller. Since the bus created by the series of bussegments is an extensible multi-drop bus, the controlled devices can beconnected to the field controller through any interface module connectedinto the field controller along the bus. Since the processor modulesegment and each expansion module segment also includes an integralhousing segment, when the processor module segment and expansion modulesegments are connected together they provide a unitary, compact housingwhich is convenient in a commercial, industrial or home environment.

BRIEF DESCRIPTION OF THE DRAWINGS

This invention is pointed out with particularity in the appended claims.The above and further advantages of this invention may be betterunderstood by referring to the following description taken inconjunction with the accompanying drawings, in which:

FIG. 1 is a functional block diagram of a distributed control systemwhich includes a field controller constructed in accordance with theinvention;

FIGS. 2A and 2B comprise functional block diagrams of the fieldcontroller subsystem useful in the distributed control system which isdepicted in FIG. 1;

FIGS. 3 and 4 are views of one embodiment of the physical structure ofthe field controller depicted in FIGS. 2A and 2B;

FIGS. 5A and 5B depict the physical structure of a processor modulecircuit structure which is useful in the field controller depicted inFIGS. 3 and 4;

FIGS. 6A and 6B depict the physical structure of an expansion modulecircuit structure which is useful in the field controller depicted inFIGS. 3 and 4;

FIGS. 7 and 8 depicts views of a second embodiment of the physicalstructure of the field controller depicted in FIGS. 2A and 2B;

FIGS. 9A and 9B depict the physical structure of a processor modulecircuit structure which is useful in the field controller depicted inFIGS. 7 and 8;

FIGS. 10A and 10B depict the physical structure of an expansion modulecircuit structure which is useful in the field controller depicted inFIGS. 7 and 8.

DETAILED DESCRIPTION OF AN ILLUSTRATIVE EMBODIMENT

FIG. 1 is a functional block diagram of a distributed control system 10which includes a field controller constructed in accordance with theinvention. The distributed control system 10 may be used, for example,in a number of commercial, industrial and home applications, inparticular to monitor and control a variety of diverse types ofoperations. For example, in a manufacturing operation, the distributedcontrol system 10 may, for example, control various machines and robotsto facilitate manufacture of those components that are manufactured onsite, and transfer of the components from inventory to assemblylocations where they are assembled into the final product. In such anoperation, the distributed control system 10 will also receive statusinformation regarding the operational status of the various machinescontrolled by the system, as well as, for example, the inventory of thevarious components which may be used in manufacture of the end productand the assembly line, which status information the system 10 may use incontrolling the rate of component manufacture and product assembly.Similarly, in a chemical processing operation, the distributed controlsystem 10 may control the rates of flow of chemicals within theoperation, as well as reaction parameters such as temperatures,pressures and the like of the chemical reaction chambers, with thecontrol being exercised in response to corresponding status informationthe system 10 receives from the controlled components of the processingplant. In a commercial or home application, the distributed controlsystem 10 may provide for the monitoring and control of a variety ofenvironmental factors, including, for example, heating, airconditioning, ventilation, energy consumption and supply, and so forth.

The distributed control system 10 depicted in FIG. 1 provides fordistributed control in a commercial, industrial or home environmentoperation. In the illustrative embodiment depicted in FIG. 1, thedistributed control system 10 includes an area controller 11 and one ormore field controllers 12(1) through 12(F) (generally identified byreference numeral 12(f)), which may be conveniently interconnected by anetwork 13 or other communications arrangement. The area controller 11maintains overall control of the industrial operation under control, ora portion thereof, thereby maintaining overall control of themanufacturing process. Each of the field controllers 12(f), undercontrol of the area controller, controls a portion of the plant, and inparticular controls specific elements of the plant, such as specificmachines (not shown) in a manufacturing operation or specific valves andreaction chambers in a chemical processing plant. In addition, eachfield controller 12(f) will receive status information preferably fromsensors (also not shown) in its assigned portion of the plant whichindicate their status in the process under control. Depending on thecontrol information and operational parameters provided by the areacontroller 11 to a field controller 12(f), the field controller 12(f)may, in response to the status information it receives from the sensorsconnected thereto, control the machines to perform selected operationsas determined by their programming. In addition, the field controller12(f) may notify the area controller 11 if the status informationindicates that operations in its area is outside of selected operationalranges, and the area controller 11 may initiate corrective procedures inconnection therewith.

FIGS. 2A and 2B together depict a functional block diagram of a fieldcontroller 12(f) useful in the distributed control system 10. Withreference initially to FIG. 2A, the field controller 12(f) 25 comprisesa plurality of modules, including a processor module 20 and one or moreexpansion modules 21(1) through 21(E) (generally identified by referencenumeral 21(e)) whose electrical features are depicted in FIGS. 2A and2B. Structural features of one embodiment of the field controller 12(f)will be described below in connection with FIGS. 3 through 6B, andstructural features of a second embodiment of the field controller 12(f)will be described below in connection with FIGS. 7 through 10B. As willbe described below, the modules 20 and 21(e) each have externalconnections which are positioned and configured to enable them to beconnected together in a relatively compact manner. In addition, themodules 20 and 21(e) provide external interfaces to control devices inthe factory environment. The entire field controller, comprising theprocessor module 20, one or more expansion modules 21(e), along withpower supply and input/output devices which may be connected thereto(not shown) provides a very compact yet computationally-powerful andeasily maintainable package, which is convenient and quite useful in anindustrial environment.

The processor module 20 comprises a processor submodule 22 and a localcommunications submodule 23. The processor submodule 22, in turn,includes a central processor unit 24, a read-only memory 25 and a mainrandom-access memory 26, all of which are connected to a bus segment 27,and may also include other components as described below. The centralprocessor unit 24 is preferably in the form of a microprocessor. Theread-only memory 25 provides non-volatile storage which may be used for,for example, a BIOS (basic input/output system) portion of the operatingsystem program that controls the central processor unit 24, and may alsoprovide storage for certain other fixed operating information. The mainrandom-access memory 26, which may consist of one or more conventionalDRAM (dynamic random-access memory) chips, provides storage for programsand data which may be down-loaded by the area controller 11 to enablethe field controller 12(f) to operate, data received from the controlleddevices and sensors controlled by the field controller 12(f),information processed by the central processor unit 24, and statusinformation which may be retained for transmission to the areacontroller. In one embodiment, the bus segment 27 conforms to thewell-known ISA bus specification, which defines a specification forbuses used in personal computers, although it will be appreciated thatbus segment 27 may conform to other multi-drop bus specifications.

In addition to components 24 through 26, the processor sub-module 22 mayinclude one or more external communication ports (generally identifiedby reference numeral 30) for, for example, facilitating communicationswith the area controller 11, devices such as light-emitting diodes,generally identified by reference numeral 31, for providing visualstatus indications, and devices for receiving local control input, suchas a reset signal provided by a reset button 32. The processorsub-module 22 may also include devices such as speakers (not shown) forgenerating audible alarm or status indications. All of these elementsare indicated as being connected to the ISA bus segment 27 over aninterface 33.

While the bus segment 27 has been described as conforming to the ISA busspecification, it will be appreciated that other types of busses may beused for the bus segment 27. Preferably, the bus segment 27 will be inthe form of a “multi-drop” bus, that is, it will facilitate theinterconnection of more than two devices to facilitate the transfer dataand status information thereamong. In addition, the bus segment 27 willpreferably provide an interrupt facility, by which the central processorunit 24 can receive interrupt requests from other devices that areconnected to the bus to notify it of conditions that may occur on anasynchronous or non-periodic basis which require servicing by thecentral processor unit 24, as will be described below.

The processor sub-module 22 in one embodiment is preferably in the formof a single module having a form factor defined by the PCMCIA (“PersonalComputer Memory Card International Association”) standard, withdimensions generally 3⅜ inches long by 2⅛ inches wide, by {fraction(1/4)} inch deep, and having an ISA bus interface preferably along oneof its long edges. A suitable processor sub-module 22 is currently soldby S-MOS Corporation as a model CARDIO™ 486 processor module, whichprovides the above-identified components and including an 80486-classmicroprocessor as the central processor unit.

The local communications sub-module 23 also includes a bus segment 40and a plurality of PCMCIA interfaces 41(1) through 41(P) (generallyidentified by reference numeral 41(p)), which are interconnected by aninterface controller chip 42. The bus segment 40 of the localcommunications sub-module 23 is logically similar to the bus segment 27of the processor sub-module 22; that is, in the embodiment in which theprocessor sub-module's bus segment 27 conforms to the ISA busspecification, the local communication sub-module's bus segment 40 willalso conform to the ISA bus specification. The local communicationssub-module's bus segment 40 connects to the processor sub-module's bussegment 27 through a downstream connector 43.

The interface controller chip 42 provides a connection from the bussegment 40 to the PCMCIA interfaces 41(p). Each PCMCIA interface inturn, provides a connection to a PCMCIA device, that is, a device whichconforms to the electrical interface defined by the PCMCIA specificationidentified above. The PCMCIA specification defines, in addition to thePCMCIA form factor described above, an electrical interface which isessentially a point-to-point bus, that is, a bus which interconnectsonly two devices. (This is in contrast to the ISA bus specificationwhich, as described above, defines a multi-drop bus, which caninterconnect more than two devices.) Each PCMCIA interface 41(p)includes an interface connector 44(p) which connects to the interfacecontroller chip 42, an interface card 45(p), and an external interface46(p) which provides an interface to a controlled device (not shown)which may be located in the industrial environment, as described above.The interface card 45(p) is preferably constructed in the PCMCIAform-factor as described above, and provides circuitry which convertsbetween PCMCIA signals provided by the interface controller chip 42 andsignals transmitted to and received from the controlled device or sensorconnected to the card 45(p). It will be appreciated that the particularcircuitry provided in each interface card 45(p) will generally depend onthe particular controlled device or sensor to which the card 45(p) isconnected.

As described above, the processor module 20 provides an interface to twocontrolled devices through the local communications sub-module 23. Toincrease the number of devices which may be controlled by the localcontroller, one or more expansion modules 21(e) may be connected to theprocessor module 20. In particular, the local communications sub-module23, in addition to providing a connector 43 to the processor module 22,also provides an upstream connector 47, which may be connected to anexpansion module 21(1), as shown in FIG. 2.

The expansion module, the physical structure of which will be describedbelow in connection with FIGS. 3, 6A and 6B, is electrically andlogically similar to the local communications sub-module 23. That is, itis provided with a downstream connector 50, a bus segment 51, anupstream connector 52, an interface controller chip 53 and a pluralityof PCMCIA interfaces 54(1) through 54(p _(e)) (generally identified byreference numeral 54(p _(e))) which include an interface connector 55(p)which connects to the interface controller chip 53, an interface card56(p), and an external interface 57(p) which provides an interface to acontrolled device (not shown) which may be located in the industrialenvironment, as described above. In one embodiment, the maximum numberof PCMCIA interfaces 54(p _(e)) that may be connected in an expansioncontroller corresponds to the number of PCMCIA interfaces 41(p) whichcan be connected in the processor sub-module 20 is two, but it will beappreciated that an expansion module 21(e) may provide more or fewerinterfaces than the processor module 20.

The downstream connector 50 of the first expansion module 21(1) connectsto the external connector 47 of the processor module 20, to connect thebus segment 51 of the first expansion module 21(1) to the bus segment 40of the local communications sub-module 23, and thus to facilitate thetransfer of signals from the processor sub-module 22 to the firstexpansion module 21(1). The bus segment 51 couples the signals from thedownstream connector 50 to the upstream connector 52 for transfer to afurther expansion module 21(2), if one is provided in the fieldcontroller 12(f). As in the local communications sub-module 23, theinterface controller chip 53 couples signals between the bus segment 51and the PCMCIA interfaces 54(p _(e)) which are provided in the firstexpansion module 21(1).

As noted above, the expansion modules 21(e) are all electrically similar(and are similar to the local communications sub-module 23 as describedabove). Accordingly, for each expansion module 21(e) after the first,the respective downstream connector 50(e) will connect to the upstreamconnector 50(e−1) of the preceding expansion module 21(e−1) in theseries, and the upstream connector 50(e) will connect to the downstreamconnector 50(e+1) of the next expansion module 21(e+1) in the series,with the module's bus segment 51(e) coupling signals between thedownstream connector 50(e) and the upstream connector 52(e). Theinterface controller chip 53(e) in the respective expansion module 21(e)connects to the bus segment 51 and the PCMCIA interfaces 54(p_(e))allowing the expansion module 21(e) to connect to a number of controlleddevices over respective PCMCIA interfaces (not shown). Since for eachexpansion module 21(e) the bus segments 27 . . . 40 . . . 51(e),interconnected by respective connectors 43, 47, 50(1), 52(1), 50(e),52(e), provide a continuous path for carrying data and control signalsfrom the central processor unit 24 of the processor sub-module 22 to therespective local communications sub-module 23 and expansion module21(e), the central processor unit 24 is able to control the controlleddevice(s) through the PCMCIA interfaces 45(p) (in the case of acontrolled device connected to the local communications sub-module 23)or 54(p_(e)) (in the case of a controlled device connected to anexpansion module 21(e).

As noted above, the expansion modules 21(e) and local communicationssub-module 23 are all electrically similar. The field controller 12(f)further includes a module selection arrangement, which will be describedin connection with FIG. 2B whereby the processor sub-module 22 canselect which of the local communications sub-module 23 or expansionmodule 21(e) is to receive signals transmitted by it (that is, theprocessor sub-module 22) on the respective bus segments 27 . . . 40 . .. 51(e), or which of the local communications sub-module 23 or expansionmodule 21(e) is to transmit signals to it (that is, the processorsub-module 22) onto the respective bus segments 27 . . . 40 . . . 51(e).With reference to FIG. 2B, in connection with the module selectionarrangement, the processor sub-module 22 generates a plurality of MODSEL module selection signals for transmission through a set ofconnectors 28(A) through 28(D), with processor sub-module 22 controllingthe pattern of asserted and negated signals so as to select one of thelocal communications sub-module 23 or an expansion module 21(e). Each ofthe local communications sub-module 23 and the expansion modules 21(e),in turn, includes a selection signal select and rotation network 29(0)through 29(3) that (a) selects a predetermined pattern of the signalsfor use in controlling selection of the local communications sub-module23 and expansion modules 21(e), and (b) rotates the signal pattern fortransmission to the next local communications sub-module 23 or expansionmodule 21(e) in the series of the local communications sub-module 23 orexpansion modules 21(e).

In the embodiment depicted in FIG. 2B, in which one local communicationssub-module 23 and three expansion modules 21(e) are provided, the fourMOD SEL module selection signals are provided, labeled A0, B0, C0 andD0. In that embodiment, the local communications sub-module 23, which isconnected directly to the processor sub-module 22, receives the MOD SELmodule selection signals A0, B0, C0 and D0, and decodes the A0 and B0signals. If the processor sub-module 22 is asserting both the MOD SELmodule selection signals A0 and B0, the local communications sub-module23 will determine that it is the “selected” module for communicationsover the bus segment 40. In any case, the local communicationssub-module 23 will rotate the MOD SEL module selection signals so thatthe signals A0, B0, C0 and D0 will be coupled to the expansion module21(1) as the signals D1, A1, B1 and C1.

The expansion module 21(1) uses the module selection signals A1 and B1to determine whether it is the “selected” module for communications overthe bus segment 51(1). As described above, the module selection signalsA1 and B1 as received by the expansion module 21(1), in turn, correspondto MOD SEL module selection signals B0 and C0, respectively, asgenerated by the processor sub-module 22. Accordingly, if the processorsub-module 22 asserts the signals B0 and C0, the expansion module 21(1)will determine that it is the “selected” module for communications overthe bus segment 51(1). In any case, the expansion module 21(1) willrotate the MOD SEL module selection signals so that the signals A1, B1,C1 and D1 will be coupled to the expansion module 21(2) as the signalsD2, A2, B2 and C2.

Similarly, the expansion module 21(2) uses the module selection signalsA2 and B2 to determine whether it is the “selected” module forcommunications over the bus segment 51(2). As described above, themodule selection signals A2 and B2 as received by the expansion module21(2), in turn, correspond to MOD SEL module selection signals C0 andD0, respectively, as generated by the processor sub-module 22.Accordingly, if the processor sub-module 22 asserts the signals C0 andD0, the expansion module 21(2) will determine that it is the “selected”module for communications over the bus segment 51(2). In any case, theexpansion module 21(2) will rotate the module selection signals so thatthe signals A2, B2, C2 and D2 will be coupled to the expansion module21(3) as the signals D3, A3, B3 and C3.

Finally, the expansion module 21(3) uses the module selection signals A3and B3 to determine whether it is the “selected” module forcommunications over the bus segment 51(3). As described above, themodule selection signals A3 and B3 as received by the expansion module21(3), in turn, correspond to MOD SEL module selection signals D0 andA0, respectively, as generated by the processor sub-module 22.Accordingly, if the processor sub-module 22 asserts the signals D0 andA0, the expansion module 21(3) will determine that it is the “selected”module for communications over the bus segment 51(3).

While FIG. 2B depicts selection of the local communications sub-module23 or one of three expansion modules 21(1) through 21(3) using four MODSEL module selection signals A0, B0, C0 and D0 as generated by theprocessor sub-module 22, by means of selection networks 29(0) through29(3) as depicted in the FIG., it will be appreciated that, by suitablemodification which will be readily apparent to those skilled in the art,module selection signals and selection networks may be provided by whichmore or fewer modules may be selected.

The field controller 12(f) which is logically depicted in FIGS. 2A and2B, provides an architecture which may be conveniently implemented in acompact package which is readily installable and maintainable in afactory environment. One embodiment of such an implementation will bedescribed in connection with FIGS. 3 through 6B, and a second embodimentwill be described in connection with FIGS. 7 through 10B. The embodimentdepicted in FIGS. 3 through 6B may be mounted on, for example, avertical support such as a wall, with the processor module 20 and eachexpansion module 21(e) being generally configured so that, when anexpansion module is added to the field controller 12(f), it will beconnected to the processor module 20 or to previously-provided expansionmodules so as to extend the field controller 12(f) in a direction whichis generally parallel to a plane of the vertical support. The embodimentdepicted in FIGS. 7 through 10B may also be mounted on a verticalsupport, but the processor module 20 and expansion modules 21(e) aregenerally configured so that, when an expansion module 21(e) is added tothe field controller, it will be connected to the processor module 20 orto previously-provided expansion modules so as to extend the fieldcontroller 12(f) in a direction which is generally transverse to a planeof the vertical support.

With reference initially to FIGS. 3 and 4, those FIGS. depictperspective views of field controllers 12(f _(A)) and 12(f _(B)) fromtwo diverse orientations, with FIG. 3 particularly depicting theprocessor module 20 component of the field controller 12(f _(A)) andFIG. 4 particularly depicting an expansion module 21(e) of fieldcontroller 12(f _(B)). The field controllers 12(f _(A)) and 12(f _(B))depicted in FIGS. 3 and 4 are generally similar except that fieldcontroller 12(f _(A)) includes a processor module 20 and one expansionmodule 21(1), whereas field controller 12(f _(B)) includes a processormodule 20 and three expansion modules 21(1) through 21(3). (Since thefield controllers 12(3). (Since the field controllers 12(f _(A)) andfield controller 12(f _(B)) are otherwise similar, they will begenerally identified hereinafter by reference numeral 12(f).) FIGS. 5Aand 5B depict opposing sides of the physical structure 60 of anelectronic circuit useful in the processor module 20 and FIGS. 6A and 6Bdepict opposing sides the physical structure 61 of an electronic circuituseful in the expansion module 21(e). It will be appreciated that theprocessor module circuit structure 60 constitutes an implementation ofthe circuit elements of the processor module 20 described above inconnection with the schematic diagram in FIG. 2, and the expansionmodule circuit structure 61 constitutes an implementation of the circuitelements of an expansion module 21(e) described above in connection withthe schematic diagram in FIG. 2.

With reference to FIGS. 3 through 6B, the field controller 12(f)includes a housing 65 having a rear mounting bracket 69 for mounting thefield controller 12(f) onto a surface such as a wall or the like. Thehousing includes a left end cap 70 (shown in FIG. 3), a series ofsegments 71(A) through 71(D) (generally identified by reference numeral71(s)) and a right end cap 72. (FIG. 3 depicts only segments 71(A) and71(B)), and FIG. 4 depicts all four segments 71(A) through 71(D)). Thesegment 71(A) is dimensioned to fit the processor module circuitstructure 60, and each of the other segments 71(B)through 71(D) isdimensioned to fit an expansion module circuit structure 61. Each of thesegments 71(s) comprises upper, lower, front and rear enclosure elements73(s) through 76(s), respectively, (lower and rear enclosure elements74(s) and 76(s) are not shown in the FIGS.) which snap togetherlaterally (that is, open-end to open-end) to, with the end caps, formcontiguous elements of a continuous enclosure. Snap fastening elementsgenerally identified by reference numeral 77 are provided to fasten thesegments 71(s) and end caps 70 and 72 together.

It will be appreciated from the description below that, in theembodiment depicted in FIGS. 3 and 4, the left end cap 70 may beprovided integrally with the segment 71(A) for the processor modulecircuit structure 60, whereas the right end cap is provided separatelyfrom any of the segments 71(s) and added to the rightmost segment. Thisresults from the fact that, in that embodiment, segments are added tothe right of the processor module segment 71(A). Since the left end cap70 will always be provided for the processor module segment, it ispreferably provided integrally with the segment 71(A).

As described above, each segment 71(s) includes upper, lower, forwardand rear enclosure elements 73(s) through 76(s), respectively,comprising the sidewalls for the segment 71(s). The lower and rearenclosure elements 75(s) and 76(s) are preferably generally planarelements, although the rear enclosure elements 76(s) may also beprovided with a fastener to receive a conventional DIN mounting rail 77.The upper enclosure elements 73(s) are preferably in the form of afinned heat sink to facilitate dissipation of thermal energy which willbe generated by the electronic circuit elements which contained withinthe enclosure. The forward enclosure elements 75(s) for the respective asegments preferably includes a number of components, including an accessdoor 80(s) and a recess 82(s) (recess 82(D) is particularly shown inFIG. 4) for receiving one or more external connectors 81(s)(A) and81(s)(B). The access doors 80(s) are hinged at the top and open upwardlyto provide access to the respective modules 20 or 21 contained thereinto facilitate insertion of components or removal for maintenance asdescribed below. In addition, the access door 80(A) of the processormodule segment 71(A) includes a connector for the external communicationport 30, the visual status indicators 31 and reset button 32, and mayalso include connectors for audible alarm indicators (not shown).

As described above, the processor module segment 71(A) is preferablyconfigured and dimensioned to receive the processor module circuitstructure 60 and each expansion module segments 71(13) through 71(D) ispreferably configured and dimensioned to receive an expansion modulecircuit structure 61. The structure of the processor module circuitstructure 60 useful in one embodiment will be described in connectionwith FIGS. 5A and 5B, and the structure of the expansion module circuitstructure useful in the same embodiment will be described in connectionwith FIGS. 6A and 6B. With reference initially to FIGS. 5A and 5B, theprocessor module circuit structure 60 includes a circuit board 90 havingmounted on one side thereof a connector 91 for receiving the processorsub-module 22 and on the other side a connector 92 for receiving thePCMCIA interface cards 45(1) and 45(2). The bus segment 27 in theprocessor sub-module 22 is internal to the processor sub-module itself,and is not depicted in FIGS. 5A and 5B. The circuit board 90 will beprovided with traces (not shown) that electrically interconnect theconnectors 91 and 92 and an off-board connector 93 (shown particularlyin FIG. 5B), to carry signals among the processor sub-module 22 andPCMCIA interface cards 45(1) and 45(2). It will be appreciated that theconnector 91 and circuit board traces generally correspond to theconnector 43 and bus segment 40 depicted in FIG. 2, and the connector 92generally corresponds to the connectors 44(1) and 44(P) shown in FIG. 2.In addition, the off-board connector 93 generally corresponds to theupstream connector 47 in FIG. 2. Circuit board 90 is also provided withconnectors and the like, generally identified by reference numeral 94,for connecting the serial port 30, visual status indicators 31 and resetbutton 32 located on the access door 85(A), and for connecting thecircuit board 90 to a power supply (not shown).

As shown in FIGS. 5A and 5B, the connectors 91 and 92 are configured sothat the processor sub-module 22 and PCMCIA interface cards 45(1) and45(2) will be positioned generally parallel to the circuit board 90 soas to provide a relatively thin package that may be convenientlypositioned in the segment 71(A) generally parallel to the left end cap71 with the off-board connector 93 being positioned toward the rearenclosure element 96(A). The off-board connector 93 corresponds to theconnector 47 (FIG. 2) and facilitates the connection between theprocessor module 20 and an expansion module 21(1). Preferably, theoff-board connector 93 provides pins and/or receptacles that areoriented generally transversely to, and towards the right of (as shownin FIGS. 5A and 5B) the plane of the circuit board 90.

With reference to FIGS. 6A and 6B, the expansion module circuitstructure 61 also includes a circuit board 100 having mounted on oneside thereof a connector 101 for receiving the PCMCIA interface cards54(1) and 54(2), and in addition includes off-board connectors 102 and103. The connector 101 is configured so that the PCMCIA interface cards54(1) and 54(2) will be positioned generally parallel to the circuitboard 90 so as to provide a relatively thin package that may beconveniently positioned in a segment 71(s) (other than the segment 71(A)for the processor module 20) with the plane of the circuit board 100being generally parallel to the plane of the circuit board 90. Off-boardconnector 102, which is situated on the left of (as shown in FIGS. 6Aand 6B) circuit board 100, includes pins and/or receptacles which areoriented generally transversely to the plane of the circuit board 100,and which mate with corresponding elements of the off-board connector 93of the processor module circuit structure 90 (FIGS. 5A and 5B).

Off-board connector 103, which is situated to the right of (as shown inFIGS. 6A and 6B) circuit board 100 is similar to the off-board connector93 of the processor sub-module, and also provides pins and/orreceptacles that are oriented generally transversely to the plane of thecircuit board 100. Since the off-board connector 103 is similar tooff-board connector 93, and since the off-board connector 102 will matewith the off-board connector 93 of the processor module 22, theoff-board connectors 102 of each successive expansion module 21(e _(B)),21(e _(c)), . . . , will also mate with the off-board connectors 103 ofthe respective previous expansion module 21(e _(A)), 21(e _(B)), . . . ,in the series of expansion modules 21(e), thereby to accommodateaddition of expansion modules as described above. It will be appreciatedthat the off-board connector 102 effectively corresponds to thedownstream connector 50 of expansion module 21(e) as described above,and the off-board 20 connector 103 effectively corresponds to itsupstream connector 52. The bus segment 51 will correspond to connectionsbetween the off-board connectors 102 and 103 on the circuit board aswell as to electrically-conductive traces interconnecting the connectors102/103 and the PCMCIA connector 101.

Returning to FIGS. 3 and 4, as noted above, the processor module circuitstructure 60 and the expansion module circuit structure(s) 61 both snapinto respective segments 71(s) of the housing 65. Each segment 71(s) isprovided with snap fastening elements 78 (shown in FIG. 4) to engage theedges of the respective circuit boards 90 (in the processor modulesegment 71(A) and 100 (in the expansion module segments 71(B) through71(D). In addition, as shown particularly in FIG. 4, each PCMCIAinterface card 45(1)/45(2) may be connected to an external connector81(s)(A) or 81(s)(B) by means of wires, such as wires 84, extending fromthe interface card, which may extend exteriorly of the segment through aslot 83(s) formed in the recess 82(s).

Since the field controller 12(f) as described above in connection withFIGS. 2 through 6B is modular, it provides a compact, expandable,easily-constructed and easily-maintainable arrangement. The fieldcontroller 12(f) may be readily assembled by snapping the processormodule circuit structure 60 (FIGS. 5A and 5B) in the segment 71(A) andany expansion module circuit structures 61 that may be required for aparticular field controller 12(f) in corresponding segments 71(B),71(C), and so forth. The external connector 30, reset switch 32 andexternal indicator 31 may be mounted on the access door 75(A) of segment71(A), and the external connectors 81(s)(A)/81(s)(B) may be mounted inthe recesses 82(s) of the respective segments. 71(s) and connected tothe PCMCIA interface cards therein. Thereafter, the respectiveconnectors 93 (of processor module circuit structure 60) and connectors102 and 103 (of expansion module circuit structure 61) will be inregistration so that, when the segments are snapped together, thedownstream connector 102 of the expansion module circuit structure 61 ina segment 71(B), 71(C), 71(D), . . . , will be in secure electricalcontact with the connector 93 of the processor module circuit structure60 in segment 71(A) or the upstream connector 103 of the expansionmodule circuit structure 61 in segment 71(B), 71(C), . . . After thelast segment 71(s) has been added, the right end cap 72 may be snappedinto place to complete the enclosure for the field controller 12(f).

It will be appreciated that a field controller can be readily expandedin the field by simple upgrading of the processor sub-module 22 and bythe easy addition of expansion modules 21(e). Addition of expansionmodules 21(e) can be readily accomplished by unsnapping of the end cap72 and snapping a new segment 71(S+1) onto the left-most segment 71(S).Since the newly-added segment's off-board connector 102 is ensured to bein registration with the connector 103 of the segment 71(S) onto whichit is being mounted, the new segment 71(S+1) is ensured to be properlyelectrically connected to the segment 71(S) and to all of the segments71(A), . . . , 71(S−1) downstream thereof. Since the PCMCIA interfacecards effectively communicate with the processor sub-module 22 over abus comprising a series of bus segments, the PCMCIA interface cardsconnected to particular controlled elements in the factory environmentcan be placed in any segment 71(s).

It will further be appreciated that the field controller 12(f) can bereadily serviced in the field. The access doors 75(s) in particular ofthe respective segments 71(s) provide ready access to the PCMCIAinterface cards 45(p) and 56(p) for service. The processor sub-module22, and the PCMCIA interface cards can be individually removed andreplaced in the field as necessary in the event of an upgrade or amalfunction through the access doors and without otherwise requiringdisassembly.

As noted above, FIGS. 7 through 10B depict a second embodiment of thefield controller 12(f), identified herein by reference numeral 112(f),in which the processor module 20 and expansion modules 21(e) aregenerally configured so that, when an expansion module 21(e) is added tothe field controller, it will be connected to the processor module 20 orto previously-provided expansion modules so as to extend the fieldcontroller 12(f) in a direction which is generally transverse to a planeof the vertical support. FIG. 7 depicts a field controller 112(f) havinga processor module 20. (In the embodiment described in FIGS. 7 through10B, the processor module 20 includes a processor sub-module 22 and twolocal communication sub-modules, one of which corresponds to the localcommunication sub-module 23 depicted in FIG. 2A, and the second localcommunication sub-module corresponding to the first expansion module21(1) depicted in FIG. 2A.) FIG. 8 depicts a field controller 112(f)′having a processor module similar to the processor module 20 of thefield controller depicted in FIG. 7, and two expansion modules 21(e),which correspond to expansion modules 21(2) and 21(3) depicted in FIGS.2A and 2B.

With reference to FIG. 7, the field controller 112(f) depicted in thatFIG. comprises a housing 120 having a rear support member 123 and acover 124. The rear support member 123 includes bracket 121 for mountingon a surface such as a wall or the like. In one particular embodiment,the bracket 121 couples onto a conventional DIN rail identified byreference numeral 122, which, in turn, may be mounted on a surface (notshown), but it will be appreciated that other mounting arrangements maybe provided for mounting the field controller 112(f).

As shown in FIG. 7, the rear support member 123 includesforwardly-extending base member 125 that includes a power connector,reset button and external connectors which are similar to thecorresponding elements 31 and 81(s)(t) described above in connectionwith the embodiment depicted in FIGS. 3 through 6B. The cover 124includes a light-emitting diode status display 126 which compriseslenses for light-emitting diodes for providing visual informationconcerning the status of the field controller 112(f), in particularwhether the field controller 112(f) is powered-up and whether it isfunctioning properly or requires servicing. In addition, the fieldcontroller 112(f) includes an access door which provides external accessto an interior connector corresponding to connector 30 described abovein connection with the embodiment depicted in FIGS. 3 through 6B. Asnoted above, the field controller 112(f) depicted in FIG. 7 includes asingle processor module circuit structure 150, which, as will bedescribed below in connection with FIGS. 9A and 9B, comprises a singlecircuit board having a processor sub-module 22 mounted on one side ofthe circuit board and two PCMCIA interface cards 45(1) and 45(2) mountedon the opposing side of the circuit board, with the planes of theprocessor sub-module 22 and PCMCIA interface cards being parallel to theplane of the circuit board. The processor module circuit structure 150is mounted interiorly of the housing 120, in particular being supportedby the rear support member 123, with the rear support member 123supporting the processor module 20 so that the plane of its circuitboard generally parallel to the rear support and mounting surface onwhich the field controller 112(f) is mounted. Wires interconnecting therespective elements of the processor module circuit structure 150 andexternal connectors are routed interiorly of the housing 120.

As described above, FIG. 8 depicts a field controller 112(f)′ having aprocessor module circuit structure 150 similar to the processor modulecircuit structure 150 of the field controller depicted in FIG. 7, andtwo expansion module circuit structures 160, which correspond toexpansion modules 21(2) and 21(3) depicted in FIGS. 2A and 2B. Withreference to FIG. 8, the field controller 112(f) depicted in that FIG.comprises a housing 130 having a rear support member 131, anintermediate member 132 and a cover 133. The rear support member 131includes a rear bracket 134 for mounting on a surface such as a wall orthe like. In one particular embodiment, the bracket 134 couples onto aconventional DIN rail identified by reference numeral 135, which, inturn, may be mounted on a surface (not shown), but it will beappreciated that other mounting arrangements may be provided formounting the field controller 112(f)′.

As shown in FIG. 8, the rear support member 131 includesforwardly-extending base member 136 that includes a power connector,reset button and external connectors which are similar to thecorresponding elements 31 and 81(s)(t) described above in connectionwith the embodiment depicted in FIGS. 3 through 6B. The intermediatemember 132 is generally similar to the rear support member 123 of thefield controller 112(f) (except that it does not provide the mountingbracket 121 provided by rear support member 123), and provides aforwardly-extending base member 137 that, in a manner similar to basemember 125 (FIG. 7), provides connectors and a reset button. The rearsupport member 131 is generally similar to support member 123 of thefield controller 11 2(f) depicted in FIG. 7, except that it is somewhatlonger so that the base member 136 will extend forwardly beneath thebase member 137 of the intermediate member. The base members 137 and 136are preferably stepped (that is, the forward surface of base member 136is somewhat rearward of the forward surface of base member 137) so thatwires connected to the connectors of the respective base members 136 and137 to provide for a relatively neat routing of the wires.

The cover 133 is generally similar to the cover 125 of the fieldcontroller 112(f) depicted in FIG. 7. In particular, the cover 133includes a light-emitting diode status display 140 which compriseslenses for light-emitting diodes for providing visual informationconcerning the status of the field controller 112(f)′, in particularwhether the field controller 112(f)′ is powered-up and whether it isfunctioning properly or requires servicing. In addition, the fieldcontroller 112(f)′ includes an access door which provides externalaccess to an interior connector corresponding to connector 30 describedabove in connection with the embodiment depicted in FIGS. 3 through 6B.As noted above, the field controller 112(f)′ depicted in FIG. 7 includesa single processor module 20 and one or more expansion modules 21(e).The processor module circuit structure 150 used in field controller112(f)′ corresponds to the module to be described below in connectionwith FIGS. 9A and 9B, and the expansion modules 21(e) will be describedbelow in connection with FIGS. 10A and 10B. As with the processor modulecircuit structure 150 used in the field controller 120, the processormodule circuit structure used in field controller 112(f)′ comprises asingle circuit board having a processor sub-module 22 mounted on oneside of the circuit board and two PCMCIA interface cards 45(1) and 45(2)mounted on the opposing side of the circuit board, with the planes ofthe processor sub-module 22 and PCMCIA interface cards being parallel tothe plane of the circuit board. Similarly, each expansion module circuitstructure 160 comprises a single circuit board having two PCMCIAinterface cards 54(1) and 54(2) mounted on one side thereof, with theplanes of the PCMCIA interface cards being parallel to the plane of thecircuit board. The processor module 20 and expansion modules 21(e) areall mounted interiorly of the housing 130, in particular being supportedby the rear support member 131, with the rear support member 131supporting the processor module circuit structure 150 and expansionmodule circuit structures 160 so that the planes of their circuit boardare generally parallel to the rear support and mounting surface on whichthe field controller 112(f)′ is mounted. Wires interconnecting therespective elements of the processor module circuit structure 150 andexpansion module circuit structures 160, and external connectors, arerouted interiorly of the housing 130.

The structure of the processor module circuit structure 150 useful inconnection with field controllers 112(f) and 112(f)′ described above inconnection with FIGS. 7 and 8 will be described in connection with FIGS.9A and 9B, and the structure of the expansion module circuit structure160 useful in the same embodiment will be described in connection withFIGS. 10A and 10B. With reference initially to FIGS. 9A and 9B, theprocessor module circuit structure 150 includes a circuit board 151having mounted on one side thereof a connector 152 for receiving theprocessor sub-module 22 and on the other side a connector 153 forreceiving the PCMCIA interface cards 45(1) and 45(2). The bus segment 27in the processor sub-module 22 is internal to the processor sub-moduleitself, and is not depicted in FIGS. 10A and 10B. The circuit board 151will be provided with traces (not shown) that electrically interconnectthe connectors 152 and 153 and an off-board connector 154 (shownparticularly in FIG. 9A), to carry signals among the processorsub-module 22 and PCMCIA interface cards 45(1) and 45(2). It will beappreciated that the connector 152 and circuit board traces generallycorrespond to the connector 43 and bus segment 40 depicted in FIG. 2A,and the connector 153 generally corresponds to the connectors 44(1) and44(P) shown in FIG. 2. In addition, the off-board connector 154generally corresponds to the upstream connector 47 in FIG. 2A. Circuitboard 151 is also provided with connectors and the like, generallyidentified by reference numeral 155, for connecting the serial port 30,visual status indicators 31 and reset button 32 located on the accessdoor 85(A), and for connecting the circuit board 90 to a power supply(not shown). In addition, the circuit board 151 supports light-emittingdiodes 156 which register with light-emitting diode status display 126or 137 to provide the above-described status indication.

As shown in FIGS. 9A and 9B, the connectors 151 and 152 are configuredso that the processor sub-module 22 and PCMCIA interface cards 45(1) and45(2) will be positioned generally parallel to the circuit board 150 soas to provide a relatively thin package that may be convenientlypositioned in the segment housing 120 or 130 as described above. Theoff-board connector 154 corresponds to the connector 47 (FIG. 2A) andfacilitates the connection between the processor module 20 and anexpansion module 21(1). Preferably, the off-board connector 93 providespins and/or receptacles that are oriented generally transversely to theplane of the circuit board 151.

With reference to FIGS. 6A and 6B, the expansion module circuitstructure 160 also includes a circuit board 161 having mounted on oneside thereof a connector 162 for receiving the PCMCIA interface cards54(1) and 54(2), and in addition includes off-board connectors 163 and164. The connector 101 is configured so that the PCMCIA interface cards54(1) and 54(2) will be positioned generally parallel to the circuitboard 160. Off-board connector 163, which is situated on the left of (asshown in FIGS. 10A and 10B) circuit board 161, includes pins and/orreceptacles which are oriented generally transversely to the plane ofthe circuit board 161, and which mate with corresponding elements of theoff-board connector 154 of the processor module circuit structure 150(FIGS. 9A and 9B).

Off-board connector 164, which is situated to the right of (as shown inFIGS. 10A and 10B) circuit board 160 is similar to the off-boardconnector 153 of the processor module circuit structure and alsoprovides pins and/or receptacles that are oriented generallytransversely to the plane of the circuit board 161. Since the off-boardconnector 164 is similar to off-board connector 153, and since theoff-board connector 164 will mate with the off-board connector 153 ofthe processor module circuit structure 150, the off-board connectors 164of each successive expansion module circuit structure 160(e _(B)), 21(e_(C)), . . . , will also mate with the off-board connectors 163 of therespective previous expansion module circuit structure 160(e _(A)), 21(e_(B)), . . . , in the series of expansion module circuit structures161(e), thereby to accommodate addition of expansion modules asdescribed above. It will be appreciated that the off-board connector 163effectively corresponds to the downstream connector 50 of expansionmodule 21(e) as described above, and the off-board connector 164effectively corresponds to its upstream connector 52. The bus segment 51will correspond to connections between the off-board connectors 163 and164 on the circuit board as well as to electrically-conductive tracesinterconnecting the connectors 163/164 and the PCMCIA connector 162.

While the invention has been described in connection with use of aprocessor sub-module 22 and interface cards having respectivecharacteristics conforming to the PCMCIA specification, such as the formfactor and (in the case of the interface cards) electrical interfacespecification, it will be appreciated that the elements may have otherform factors and interface specifications. It is preferable, however,that the elements have generally the same form factors, and bepreferably relatively thin so that the segments 71(s) may be relativelythin facilitating relatively tight packing. In addition, will bepreferable that any bus comprising bus segments 27, 40, and 51 be amulti-drop bus so that the PCMCIA interface cards for the variouscontrolled devices can be connected anywhere along the bus.

In addition, while the new field controller 12(f) (as well as fieldcontrollers 112(f) and 112(f′)) has been described as operating in adistributed control system 10 under control of an area controller 11, itwill be appreciated that, depending on the particular application, areacontroller may not be necessary and the field controller may operateindependently. In addition, it will be appreciated that a variety ofdevices may be controlled by a field controller as described herein,including other field controllers.

The foregoing description has been limited to a specific embodiment ofthis invention. It will be apparent, however, that various variationsand modifications may be made to the invention, with the attainment ofsome or all of the advantages of the invention. It is the object of theappended claims to cover these and such other variations andmodifications as come within the true spirit and scope of the invention.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:
 1. A process control system comprising one or moreindustrial computing devices that include a field mountable housing; aprocessor, said processor being internal to said housing; at least oneperipheral connector adapted to receive at least one PCMCIA card suchthat when said PCMCIA card is plugged into said peripheral connector,said PCMCIA card is enclosed internal to said housing, said peripheralconnector being electrically coupled to said processor, wherein saidindustrial computing device is self contained and without full user I/Oin that said industrial computing device is without at least one of afull display and a full keyboard; a first PCMCIA card plugged into afirst peripheral connector of said at least one peripheral connector;and an electrical connector attached to said first PCMCIA card by acable, said cable being internal to said housing, said electricalconnector being accessible external to said housing.
 2. A processcontrol system comprising: one or more industrial computing devices thatinclude a field mountable housing; a processor, said processor beinginternal to said housing; and at least one peripheral connector adaptedto receive at least one PCMCIA card such that when said PCMCIA card isplugged into said peripheral connector, said PCMCIA card is enclosedinternal to said housing, said peripheral connector being electricallycoupled to said processor, wherein said industrial computing device isself contained and without full user I/O in that said industrialcomputing device is without at least one of a full display and a fullkeyboard; a first PCMCIA card plugged into a first peripheral connectorof said at least one peripheral connector; and an electrical connectorattached to said first PCMCIA card by a cable, said cable being internalto said housing, said electrical connector being accessible external tosaid housing, wherein said electrical connector is flush mounted to saidhousing.
 3. A process control system comprising: one or more industrialcomputing devices that include a field mountable housing; a processor,said processor being internal to said housing; and at least oneperipheral connector adapted to receive at least one PCMCIA card suchthat when said PCMCIA card is plugged into said peripheral connector,said PCMCIA card is enclosed internal to said housing, said peripheralconnector being electrically coupled to said processor, wherein saidindustrial computing device is self contained and without full user I/Oin that said industrial computing device is without at least one of afull display and a full keyboard, wherein said processor and said atleast one peripheral connector are disposed on a common circuit boardand wherein said processor and said at least one peripheral connectorare disposed on opposite sides of said common circuit board.
 4. Aprocess control system comprising one or more industrial computingdevices that include a field mountable housing; a processor, saidprocessor being internal to said housing; and at least one peripheralconnector adapted to receive at least one PCMCIA card such that whensaid PCMCIA card is plugged into said peripheral connector, said PCMCIAcard is enclosed internal to said housing, said peripheral connectorbeing electrically coupled to said processor, and wherein said processorand said at least one peripheral connector are disposed on oppositesides of a common circuit board.